U.S. Pat. No. 8,738,278 (the '278 patent) to Shane Chen, the inventor herein, discloses a Two-Wheel Self-Balancing Vehicle with Independently Movable Foot Placement Sections. This patent is hereby incorporated by reference as though disclosed in its entirety herein.
Since the development and disclosure of the device of the '278 patent, knock-off devices have been manufactured and widely marketed. In popular culture, these devices may be referred to as “hoverboards.”
The devices are battery powered. In an effort to conserve power and to quickly stop the device when a rider dismounts (or falls off), the devices may include a foot sensor that is configured along with their associated control electronics to turn off self-balancing when a rider is no longer on the platform. This arrangement conserves power.
One type of prior art foot sensor is a pressure (or weight based) sensor, detecting when a user is standing on the platform. These sensors are typically mounted to the surface of the foot platform and include an internally disposed movable member. When weight is applied to the sensors, the movable member is displaced such that it activates a transducer or breaks a light beam, etc., to generate a signal. Various pressure sensors are known in the art.
The pressure sensors are disadvantageous in that they include a moving part and thus are more likely to fail. They are also disadvantageous in that, in the context of a self-balancing transportation device, they require sufficient pressure precisely delivered to the sensor. When (re)activating the device, this may necessitate a rider bending over and holding the device while attempting to apply pressure of sufficient force and direction to trip the sensor, or awkwardly hooking the device with one foot and trying to apply that pressure.
Another type of sensor is a proximity sensor. Proximity sensors typically consist of an emitter and a co-housed detector. They emit electro-magnetic radiation and detect radiation that is reflected back. Infrared is a known type of electro-magnetic radiation, among others, used in proximity sensors.
The infrared proximity sensors, however, are disadvantageous in that when shoes are worn that are not sufficiently reflective, for example, duller black shoes, there is insufficient reflection for the sensor to function properly. Thus, they may falsely indicate the absence of a rider and de-activate self-balancing with a dull, dark shoed rider is actually on the device.
Hence, a need exists for a foot sensor arrangement for a self-balancing personal transportation device that has no or fewer moving parts, works regardless of the reflectivity of the rider's footwear, and/or that allows a user to activate self-balancing in an ergonomically-friendly manner, i.e., without a rider bending over or awkwardly trying to position the device for mounting, among other needs.